Wastes from the daily lives of households and commercial establishments involved in eating and drinking such as restaurants and shops contain a large amount of water. The present invention relates to methods for processing wastes containing a large amount of water prior to incineration in order to burn the wastes efficiently, specifically to the processes such as drying, disintegrating, and sorting the wastes, prior to incineration.
The present invention also relates to methods that prevent toxic metals, such as heavy metals contained in industrial and non-industrial wastes, from discharging into the local environment around the waste processing plant, to protect the environment from the contamination.
Industrial wastes and non-industrial wastes end up with reclamation sites along the seashore, landfill sites in an inland area, and incinerators. However, wastes are not dumped for reclamation sites along the seashore forever, because reclamation from the sea is environmentally problematic and the more the wastes are dumped, the smaller the dumping sites.
The incinerator is costly because of an initial cost of building the plant and the running cost of the plant including the labor cost. In addition, the site to build the plant is limited because the incinerator produces unpleasant odors, toxic waste gases, airborne particles, and burned ashes. Another problem of the incinerator is the incinerator itself. The incinerator is required to increase its capacity in order to completely burn a large amount of garbage. However, complete combustion of a large amount of garbage is economically unfavorable.
Industrial wastes contain metals. Metals, especially heavy metals, have played an important role in various fields and contributed to technological development. Once metals complete their role, however, most of them are typically disposed in landfill sites as industrial wastes except that the removal of metals from the wastes is economically feasible. When disposed, heavy metals could become harmful to people and potentially cause various disorders. The trace amount of heavy metals contaminates the environment and the contamination draws a special attention in our society.
The present inventors previously filed the invention directed to the method for removing toxic substances from the leachate from burned ashes containing toxic heavy metals, the method that are used to process industrial and non-industrial wastes (Japanese Patent Application No. 96995/1991). The present inventors also filed the invention directed to the method for preventing environmental contamination in the surrounding area of the waste processing plant by processing toxic-components-containing wastewater produced in the waste processing plant and processing the wastewater in the plant without discharging it to the outside environment (Japanese Patent Application No. 81178/1992).
In order to prevent the discharge of environmental contaminants such as heavy metals contained in industrial wastes and their ashes, the first previous invention was directed to the method for preventing the discharge of the environmental contaminants by placing the industrial wastes in a soil layer built under the ground to confine the industrial wastes, the soil layer that is composed of a mixture of volcanic ash soil and alluvial soil. The toxic substance content in the leachate from the structure is lower than the standard established by the Ministry of Welfare and is found to be safe to be discharged in rivers.